In a futuristic reunified Korea where robots serve as second-class citizens, estranged siblings Jun and Morgan are drawn together by a mystery surrounding their long-lost brother, Yoyo—an unusually humanlike robot. As Jun investigates a case for the Robot Crimes Unit and Morgan prepares to unveil her most advanced creation, an ailing girl named Ruijie discovers Yoyo in a junkyard, forging a powerful bond. As past secrets surface and their paths collide, the siblings must confront their shared history and what it truly means to be human.